We conducted a study on excessive doping of the Cr and In elements in Bi-Sb-Te materials satisfying the Hume- Rothery rule, and investigated the resulting electrical and thermal properties. From X-ray diffraction (XRD) results, we confirmed the formation of a single phase even with excessive doping. Through analysis of electrical properties, we observed the highest enhancement in electrical characteristics at y = 0.2, suggesting that the appropriate ratio of Bi-Sb significantly influences this enhancement. Using the Callaway-von Baeyer (CvB) model to assess scattering due to point defects, we calculated the experimental point defect scattering factor (ΓCvB.exp), which was notably high due to the substantial differences in volume and atomic weight between the substituted (Cr, In) and original (Bi, Sb) elements. Additionally, we conducted a single parabolic band (SPB) modeling analysis of materials with compositions y = 0.1 and 0.2, where, despite a decrease in densityof- states effective mass (md *) during the enhancement process from y = 0.1 to 0.2, a sharp increase in non-degenerate mobility (μ0) led to an 88 % increase in weighted mobility (μw). Furthermore, analyzing zT with respect to nH revealed a 51 % increase in zT at a composition of y = 0.2. This study confirmed a significant reduction in lattice thermal conductivity with the co-doping strategy, and with further compositional studies to improve electrical properties, we anticipate achieving high zT.

필자는 교차편년으로 설정된 기존의 남한 원형점토대토기문화의 연대와 출현 과정에 오류가 있음 을 발견하였다. 이에 방사성탄소연대를 이용해 기존의 견해와 다른 새로운 연대 안과 출현과정을 제 시하고자 하였다. 또한 현재 학계에 뚜렷한 견해가 없는 원형점토대토기문화의 성격에 대하여도 새로 운 시각으로 접근하여 원형점토대토기문화의 실체를 규명하고자 하였다. 그 결과는 다음과 같다. 남한 원형점토대토기는 BC 12세기 무렵, 비파형동검과 동시에 출현하였으며, 이후 후기 청동기시 대 송국리문화, 역삼동후기문화, 검단리문화 등과 기원전 2세기 무렵까지 장기간에 걸쳐 공존하였다. 남한 원형점토대토기문화 집단은 요동지역‘정치집단’의 이주민이 아니라 청동기시대 조기부터 형성 되어 있던‘요동-서북한-남한’의 네트워크를 통해 남한에 들어온‘청동장인집단’이다. 이들이 남겨 놓은 유적 중‘수석리유적’,‘교성리유적’등은 당시 청동의 원광석을 채광·선광했던 장소로 추정 되며,‘동학산유적’,‘방동리유적’등은 청동을 제련·주조 했던 장소로 추정된다. 이‘청동장인집단’은 재지 사회의 지배층에게 비파형동검 등의 청동기를 제작·공급해서 생계를 유지하던 기술장인들이었으나 점차 정치력을 갖게 되면서 세형동검단계에 이르러서는 당시 사회의 지 배층인‘제사장’이되고, 결국 삼한 사회의 최상위 지배층으로 성장한다.

In this study, a finite element analysis was used to analyze the stress state and vibration characteristics generated by continuous contact between wheels and rails when driving urban railway vehicles. The rails applied to the analysis were divided into straight and curved shapes, and three-dimensional modeling was performed to analyze the changes in structural characteristics of wheels and rails when driving on straight and curved rails. As a result of the analysis, the stress characteristics were up to 6.5 MPa on a straight rail and 9.81 MPa on a curved rail, and it is believed that this increase in stress will increase noise due to an increase in friction at the interface. The vibration characteristics of the wheels and rails showed similar behavior from the 3rd mode to the 9th mode of the rail to the intrinsic vibration characteristics from the 4th mode to the 6th mode of the wheel.

The most important factor in the processing of composite materials is the creation of burrs. In order to minimize the generation of burrs, the preceding researchers changed the shape and processing conditions of the tool. The developed composite material using carbon and aramid fibers has limitations in reducing the formation of burrs. In this study, in order to solve this problem, by applying a jig under the test piece during drilling, it was possible to perform high-quality hole processing with minimal burr generation.

In this study, we compare and analyze stress and vertical deflectional displacement according to cross sectional shape changes of the beam using finite element analysis. The 11,000mm long horizontal beam showed stress differences depending on the cross-sectional variation, with stress differences of up to 200MPa and at least 149MPa. The deflection at the end of the beam also differed by up to 586 mm and at least 208mm. The weight change applied according to the cross-sectional shape of the steel horizontal beam was up to 235kgf, at least 144kgf, and showed the best stress and deflection characteristics in the cross sectional shape with a weight of 185kgf. This allowed us to improve structural safety through sectional shape optimization despite the weight increase.

PURPOSES : This study deals with a pressure relief joint, which is one of primary preventive methods of blow-up in concrete pavement. The purpose of the study is to estimate the joint sealant protrusion of pressure relief joint filler types according to horizontal displacement of concrete pavement by applying a variety of joint sealants and joint fillers. And test method for resistance of concrete to chloride ion penetration and test method for resistance of concrete to rapid freezing and thawing were conducted to analyze the improvement of concrete durability according to the primer types on concrete surface of stress relief joint. METHODS : Joint fillers of pressure relief joint were categorized into four different types, which are was styrofoam+backer+sealant(type 1), styrofoam+sealant(type 2), foaming styrofoam+sealant(type 3), and preformed joint+sealant(type 4). By varying the depth (10, 20, 30, 50 mm) from the top of the test specimens to the sealant’s surface, the test factors were evaluated for a total of 16 variables. When the specimen’s joint spacing decreased from 70mm to 10mm, the load was stopped. And the displacement of the center of the joint protrusion was measured. The test was terminated when the specimen joint spacing was reduced to 60 mm. The horizontal displacement at the time when the joint protrudes over the specimen surface is recorded and analyzed as the critical threshold displacement. RESULTS : According to the test results according to the type of joint filling material, it was found that there was a difference in the protrusion of the horizontal compression displacement according to the joint filling type. Under the current installation standard of 20mm, the preformed seal joint member showed the best crimping characteristics by securing the safety against protrusion until the horizontal displacement of 50mm occurred. CONCLUSIONS : The most common failures in pressure relief joints are those related to joint sealants, which can be minimized by changing the current joint type, installation depth, etc. to suppress them.